I am so sorry to hear about your dad, I lost mum 7 years ago to breast cancer and the day after gave birth to my first daughter. My dad has now been diagonosed with advanced small cell lung cancer which as spead to his liver, skin and lymph.
I know exactly what you are going through my mum had a very short fight of just 5 months and was very ill and weak through the whole thing.
People never seam to know what to say when you have lost anyone close but all I can say is that he will be watching and he will still be there part of your lives. I feel mum with me all the time and just the other day infact the day dad was home from his chemo he was resting and suddendley felt a hand on his sholder and a kiss on his forehead and noboy was in and dad says it was mum kissing him good night. So be rest assured that you dad is not far away watching over the family.
My thoughts are with your family at this very sad time.
Siobhan